Yes, of course. I want to rename the argument of
`set-face-underline-p' (and `modify-face').
I usually wouldn't have asked just to change this; but sometimes
people complains when arguments are changed, and in this case
`set-face-underline-p' is part of a family of functions, all of which
have arguments like BOLD-P, ITALIC-P, etc. But these really are
boolean, so clarity and correctness should weight more than
(pseudo-)consistency.

BTW, in my version (from 2007-01-25), the arg name in the signature is
`underline-p', but it is referred to in the doc string as UNDERLINE.

Yes, that's how I found the problem. It's not a typo in the docstring,
but the result of conflating two previous defuns, one of them
`set-face-underline', without -p (which had a non-flag UNDERLINE
argument), the other named `set-face-underline-p' and with a boolean
UNDERLINE-P argument.
/L/e/k/t/u